Cellulosic fibers such as cotton, rayon and lyocell are used in the manufacture of textiles and non-wovens.
The conventional method for the commercial preparation of cellulosic fibers is the viscose process. In one of the conventional processes for the manufacture of cellulosic fibers, cellulose prepared from either wood pulp, is treated with sodium hydroxide and then with carbon disulfide to form cellulose xanthate. The cellulose xanthate thus formed is dissolved in dilute solution of sodium hydroxide to obtain a thick solution called viscose. The viscose is then forced through tiny openings in a spinneret into an acid solution, which coagulates it in the form of fine strands of fibers. In the wet spinning method, the process involves spinning of polymer dope directly into a liquid bath. The cellulosic fibers obtained from the viscose process are non-fibrillating, but possess low strength. Further, the viscose process involves the use of hazardous liquids such as carbon disulfide and sulphuric acid thus making entire process not environment friendly.
In another conventional process for manufacturing cellulosic fibers, cellulose is dissolved in a cupramonium solution to form a solution which is forced through submerged spinnerets into a dilute sulphuric acid, which acts as coagulating agent, to form fibers. The main drawback of the process is that efficient ammonia recovery is difficult to achieve and the process is more expensive than the viscose rayon process.
The cellulose/lyocell fibers are also known to be obtained using a dry jet wet spinning technique using N-methylmorpholine N-oxide hydrate. Although, the dry jet wet spinning process gives significantly higher fiber tenacity and modulus than the conventional wet jet spinning process, the use of NMMO is not desirable due to the fact that NMMO is thermally unstable and is explosive at higher temperature leading to its degradation and generation of coloured compounds that affects the whiteness of the fibers and increasing the cost of the fiber and the fiber prepared from the above process show high fibrillation tendency, which affects the appearance of the product made from such fibers. Further, to reduce the fibrillation tendency, the conventional fibers are required to be further processed by cross-linking agents or by mechanical, chemical or enzymatic means which further add to the cost of the overall process.
WO 2009/062723 of BASF published on May 22, 2009, relates to a spinning process and discloses use of EMIM octanoate and imidazolium-dialkylphosphates.
WO 2006/000197 and WO 2007/128268 of TITK disclose a spinning process of cellulose in ionic liquid.
WO 2008/133269 of Nisshinbo Industries discloses ionic liquids, wherein the cation (including imidazolium) has at least one alkoxyalkyl group and the anion is dimethyl phosphate and has good solubility of cellulose and fibers are mentioned without any details or examples.
WO2007076979 of BASF discloses a solution system for biopolymers in the form of carbohydrates, solution system containing molten ionic liquid, also additives optionally being contained in the solution system, is described. This solution system contains a protic solvent or a mixture of several protic solvents, and in the case where the protic solvent is solely water, it is present in the solution system in an amount of more than about 5 wt. %. The patent provides a process for regenerated cellulose non-fibrillating spun fibers.
There is, therefore, a need to develop a process, for preparing non-fibrillating cellulosic fibers, which is simple, cost effective, environment friendly and which can overcome the shortcomings of the conventional processes without requiring the use of harmful solvents. The current disclosure describes a process of manufacturing low fibrillating cellulosic fibers using dry-jet-wet spinning under specific spinning conditions using ionic liquids as solvents for cellulose.